HEALTH

HEALTH; Prenatal Test For Defects Termed Safe In U.S. Study

By GINA KOLATA

Published: May 5, 1988

An experimental prenatal test that can identify common birth defects after 9 1/2 to 12 weeks of pregnancy is nearly as safe as amniocentesis, according to a Federal study.

The new method, chorionic villus sampling, or C.V.S., is offered in about 20 medical centers in the United States and has only been done for about four years. To do C.V.S., doctors remove small amounts of tissue that surrounds the fetus early in pregnancy and analyze the fetal cells for evidence of genetic abnormalities.

An advantage of the method is that it is done in the first trimester of pregnancy, so that if a woman finds that her fetus has a serious birth defect and chooses to abort, an abortion is still relatively safe. But many doctors have hesitated to offer C.V.S. because they feared it might cause too many miscarriages.

The most common method, amniocentesis, has been used for two decades and is generally considered safe. It involves removing amniotic fluid that bathes the fetus and analyzing the fetal cells that float in the fluid. But a disadvantage is that it is performed at about 16 weeks of pregnancy, when abortions are more difficult medically and emotionally. Both Detect Genetic Defects

Both procedures can accurately detect fetuses with Down's syndrome, the most common inherited cause of mental retardation, and other genetic defects.

The new study, directed by Dr. George Rhoads of the National Institute of Child Health and Human Development, involved 2,278 women who received C.V.S. and 671 who received amniocentesis. Two percent of the C.V.S. patients miscarried and 1.3 percent of the amniocentesis patients miscarried, but the scientists said it was not clear whether the small difference was statistically significant.

Dr. Ronald Wapner of Thomans Jefferson Univeristy in Philadelphia, who participated in the study, predicted that C.V.S. would be more widely used now that there were good data on its safety. The study, he said, ''should make people much more comfortable with C.V.S. - it shows C.V.S. is not dangerous.''

In addition, Dr. Wapner said, the study showed that ''the risk of infection with C.V.S. is very very low -significantly less than 1 percent.''